[FallenAngel]

Quote:

Originally Posted by slaikan /img/forum/go_quote.gif Hi Finished building the PPA v2, very very happy with it, no problems with the build which I'm thankful for since its only my third DIY project. First was the CMOY (recently destroyed the OPA2132 with reverse polarity... oops), then the Audiosector Premium USB DAC and now the PPA. I struggled more with the casing and getting everything to fit properly than bulding the PPA itself. I used all the standard components off the Tangent parts list except for C5's are WIMA MKS4 250V 0.1uF as thats all I could find in a hurry at the time. For those who have experience with different caps, should I replace them with WIMA MKS2 63V 1uF or maybe something else and how much do these caps affect sound quality? I'm using Panasonic FM throughout, 220uF 35V caps on the input side and 3x 680uF 35V on the power supply side. Is there a significant difference with 'boutique' caps like Blackgates, Nichicon Muse, Elna Silmic etc. cause its quite difficult to get that where I stay, so it all needs to be imported. What are you opinions of using CAT5e for hookup wire, thats what I'm using at the moment, I decided not to import fancy hookup wire and my perferred local supplier only sells hookup wire in 20 meter reels, per colour... Thanks

Congrats, it's a very nice amp.

For the PSU caps, using electrolytic caps made for signal coupling is not recommended (BlackGate N, Muse ES, etc). Going with Elna Silmic II is definitely an option, but I personally wouldn't bother with going above Panasonic FM, they're very good PSU caps.

Cat5e is also OK, but not the best. I would recommend using a nicer wire like surplus SPC from eBay (Silver Plated Copper) - it's cheap and sounds much better.

 

[luvdunhill]

hey, is there an easy way to verify that Tangent's crossfeed board is working as designed? I'm using a rotary switch in the "simple" configuration.

 

[StanRex]

Mmm, I'm getting confused.

I've removed all the unnecessary input and output wiring, and have done some tests.

Voltage at the power supply pins of the opamps is ok. I get 11.5 between V+and ground and the same between V- and ground when no opamp is in the socket. With an opamp, I get lower values (I think 11.1) but I think it's normal

Anyway,

Yesterday, I had a working ground channel with an AD8610 in it. It gave reasonable voltage readings at the output resistor (30mV or so)

I swapped the opamps a few times between the supposedly working right channel and ground.

And somehow, I ended up with 0 channels working.
I believe my AD8610 all fried

I don't understand how it happened. I'm thinking it could be because the browndog adapters dont have a good fit in the sockets, so it could have caused some of the opamps pins not to connect properly with the socket. But not sure such a thing could fry the opamps

anyway

Since I've lost a faire share of useful opamps, I ve decided to do the rest of the "risky" (risky as in "can blow the opamps") testing with my DIP8 AD843.

I ve put an AD843 in the ground socket. Works ok. Get 30mV at the output resistor. Then I ve tried putting in the right channel socket. Ok once more. I'm going to replace Q24 and 34 before doing the same with the left channel (I'm pretty sure one of them burnt during a previous experiment)

So far, I haven't dared try with two AD843, one in the right channel and one in the ground (the two channels that work at the moment), because when I had tried doing so with the AD8610, they had died. Was it just bad luck/bad contacts between the opamp pins, or is it possible that these channel work OK when used seperately, but will somehow fry the opamps when used at the same time?

Thanks in advance for your answer

ps : I also have some DIP8 OPA627, but I d rather do the risky testing with the AD843 before taking chances with the 627, considering their price tag...

 

[slaikan]

Thanks FallenAngel, it is a very nice amp, HD595's haven't sounded as good they sound now, I only have the CMOY and the output of a Zune and Sony NW-HD5 to compare with though. I guess I'll be shopping for better hookup wire, I'll be keeping the PSU caps as you've recommended.

What about the Panasonic FM 220uF caps in C4 and the 0.1uF WIMA's in C5, should I toy with them or just leave them as is?

Thanks

 

[StanRex]

I've replaced the output transistors of the left channel, found there was a bit of solder (causing a short) between two legs of one of them, could be what had caused me trouble

anyway, I replaced those. Put my "official tester" (AD834) in the socket, switched the amp on and checked voltages at the output resistor. Woohoo! 30mV! Got it to 44mV, like the others.

Now, I'm going to start with one OPA627 in the ground channel, see if voltage at the output resistor is ok.

If it is, I'll take the leap of faith and put all my 3 DIP OPA627 in the sockets. I really hope I wont fry them though ^^

edit : tried. Nothing fried. Adjusted the bias. Then checked DC offset. 1 and 4 mV for ground and right channel, but left channel exhibits 17mV between OL and IG. I'm going to try cleaning things up a bit

edit 2 : I've tried cleaning and reflowing a few joints, but it didn't lower the offset. could the dc offset be caused by unmatched output transistors? I tried matching the buffer transistors, but not the output ones. Anyway, I think I read that something under 20mV isn't perfect but is acceptable . So I guess I'll just move on.

 

[StanRex]

just a quick question: how exactly do you get the ground strap to stick to the alps pot? I ve tried solder, solder with flux, but nothing gets solder to stick to the damn vise of the pot...

 

[slaikan]

For mine, I just unscrewed the corner screw a little, filed it a bit to make it a little rough, soldering was a little easier after that.

 

[MisterX]

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif hey, is there an easy way to verify that Tangent's crossfeed board is working as designed? I'm using a rotary switch in the "simple" configuration.

Mute or disconnect one of the channels.

 

[StanRex]

I'm too tired so I'll stop working on the PPA for today. Anyway, progress report since last weekend :

ppa doesnt kill opamps anymore
I have 40mV or so at each output resistor (so technically, I think each channel is working)

on the todo list :

fix the output :

no source connected, ****ty earbuds (connected through a 6.35 to 3.5 adapter) on the output
The ppa outputs noise. Lots of noise. I think it should be dead silent instead. Groundstrapping the pot didn't help. Anyway what's surprising is that at the lowest pot setting, noise level is very high. I haven't tried increasing the volume, but it s already more than audible at the lowest position of the pot

(I'm using 3 opa627)

 

[espressogeek]

StanRex,
I am very sorry to hear of your PPAv2 woes. What type of noise are you hearing? I only had noise on mine , ground hum type noise, when touching the unstrapped pot. Once I strapped it everything was OK.

What type of power supply are you using?

 

[StanRex]

I m using a TREAD for PS. For the noise, I ve put the ground strap, but it doesn't change anything. And I dont need to touch the pot. In fact, wether I touch it or not, it doesn't change anything.

There s just a lot of noise, that can be heard even though no source is connected. And the noise level goes up to a unlistenable (too loud) level if I increase the volume using the pot

 

[FallenAngel]

Quote:

Originally Posted by slaikan /img/forum/go_quote.gif Thanks FallenAngel, it is a very nice amp, HD595's haven't sounded as good they sound now, I only have the CMOY and the output of a Zune and Sony NW-HD5 to compare with though. I guess I'll be shopping for better hookup wire, I'll be keeping the PSU caps as you've recommended. What about the Panasonic FM 220uF caps in C4 and the 0.1uF WIMA's in C5, should I toy with them or just leave them as is? Thanks

I wouldn't touch them, the caps are very nice and unless you want "audiophile" parts, you won't find better. Just not worth the trouble to replace them.

Quote:

Originally Posted by StanRex /img/forum/go_quote.gif edit : tried. Nothing fried. Adjusted the bias. Then checked DC offset. 1 and 4 mV for ground and right channel, but left channel exhibits 17mV between OL and IG. I'm going to try cleaning things up a bit edit 2 : I've tried cleaning and reflowing a few joints, but it didn't lower the offset. could the dc offset be caused by unmatched output transistors? I tried matching the buffer transistors, but not the output ones. Anyway, I think I read that something under 20mV isn't perfect but is acceptable . So I guess I'll just move on.

You're suppose to measure offset between OR/OL and OG (not IG).

Can you measure AC on the output of your TREAD to make sure it's non-existent?

What's the current draw on the amp?

 

[slaikan]

StanRex, hang in there, it seems like its coming right. Now I'm far from being qualified compared to other posters here, I had some hissing and buzzing with my build, but grounding the pot, moving the PPA away from exposed transformers (which is probably a possibility during assemly) and adjusting the right bias all helped. I found that during testing, I heard hiss on my cheap IEM's at all levels, once I was confident enough to plug in the more expensive headphones, the hiss decreased drastically, once everything is in the right place, adjusted correctly, etc. the hiss completely went away, except at close to max volume.

Oh, I accidently swopped the ground and left channel, lots of hiss, and had loads of echo which was interesting, but once I found my mistake, everything just came right.

Good luck, hope it comes right soon.

 

[slaikan]

FallenAngel, thanks again. I guess I'll sit back and simply enjoy the music.... until the DIY and upgrade bug bites again in a few months, or weeks

Just just some final things, screw down the tread, close up the cases, sort out the knobs, and we're done... for now

 

[espressogeek]

Quick question for all of you experienced DIY'ers, What size and type standoffs do you use to mount your PPAv2 in a non Hammond case. Also, what case options are considered the best? I am thinking of mounting this in a case with a toroid and tread.

Thanks in advance